1. Field of the Invention
The present invention relates to a solid electrolyte used for a cell, a sensor such as an ionic sensor and an electrochemical display element and the like and more particularly to an ionic conductor in which fluoride ions conduct.
2. Description of the Prior Art
A fluoride ionic conductor such as .beta.-PbF.sub.2, CaF.sub.2, LaF.sub.3, and the like have been generally known. The electrolytic conductivity (the ionic conductivity) of these materials is about 10.sup.-6 S/cm at room temperature. Recently Reau et al. have found that PbSnF.sub.4 has a high ionic conductivity of 10.sup.-3 S/cm.
A cell, an ionic sensor and the like are suggested as elements using these fluoride ionic conductors.
In an ionic conductor of a solid electrolyte, an excellent ionic conductivity at room temperature is particularly desirable, because when an electrochemical element such as a cell, a sensor, an electrochemical display element and the like is made of the solid electrolyte, the ionic conductivity is related with the inside impedance of the element: The excellent ionic conductivity of the solid electrolyte makes the inside impedance of the electrochemical element formed thereby low. On the contrary, poor ionic conductivity makes the inside impedance high, resulting in deteriorating discharge efficiency in a cell, and slowing speed of response in a sensor and an electrochemical display element. Therefore, the ionic conductivity of the solid electrolyte needs to be improved at room temperature.
The present invention provides a fluoride ionic conductor with improved ionic conductivity.